1. Field of the Invention
The present invention relates to apparatus for spraying plants with agricultural solutions such as pesticides or fungicides, and more particularly, it concerns an air sprayer for row crops of low or medium height, such as trellissed grapevines and the like, which employs an air blast to deliver atomized spray solution throughout the foliage and fruits of the plants.
2. Description of the Prior Art
Air sprayers, or air blast sprayers, have been employed for many years to apply pesticides, fungicides and other agricultural liquid solutions to the foliage and fruits of orchards, groves and vineyards. An air sprayer generally employs a liquid flow system and an air flow system designed to work together to deliver a controlled air-spray pattern which penetrates the foliage and fruits of a plant. The liquid flow system of the sprayer includes a holding or spray tank mounted on a trailer frame, a plurality of spray nozzles, a pump which is driven by the power take-off of the tractor which pulls the spray trailer, and conduits and valving for delivering the spray solution from the tank to the pump and subsequently to the nozzles under regulated pressure. The air flow system employs a blower assembly having at least one discharge opening for directing an air blast generally transversely of the path of travel of the sprayer. The spray nozzles are disposed in the discharge opening to deliver atomized spray solution for entrainment in the air blast.
One known type of air sprayer for spraying vineyards includes a centrifugal or squirrel cage fan which is disposed behind the spray tank on the sprayer trailer. The centrifugal fan includes a housing having air inlet openings oriented transversely of the path of travel of the sprayer, and an outlet opening extending rearwardly and longitudinally of the sprayer's path of travel. Normally, a pair of deflector housings are connected to each outlet opening. Each deflector housing has a "fish tail" shape and has an arcuate discharge opening which extends transversely of the sprayer. The arcuate opening is vertically oriented and is adapted to deliver an air blast extending over a vertical, widely diverging pattern. Typically, the deflector housings are adjustably mounted to the respective centrifugal fans so that the air blasts may be directed at various angles relative to the horizontal. This type of sprayer is normally used to spray two rows of vines at one time, the deflector housings being adjusted to direct the air blasts in opposite transverse directions relative to the path of movement of the sprayer. A major problem associated with this type of sprayer is that the high velocity air blast from each deflector housing discharge opening tends to cause the broad leaves of grapevines to "shingle", that is, to lie flat against each other so as to prevent the spray solution from penetrating through the leaves.
It is also known that the centrifugal type of fan sprayer may be employed to provide two air blasts against a single row of grapevines. This is accomplished by mounting two deflector housings in series to each centrifugal fan and by positioning the deflector housings at different rotative positions so as to extend at different angles toward one side of the sprayer trailer. It should be noted that due to the widely diverging, vertical spread of each of the two air blasts emanating from the separate openings, it is not possible to adjust the deflector housings at substantially different angles, because to do so would mean that a substantial portion of at least one of the air blasts would be directed either toward the ground or above the plants to be sprayed. Thus, the air blasts from the separate deflectors impinge upon the foliage at essentially the same angle. The aforementioned "shingling" problem is not obviated by such separate air blasts.
Another known type of vineyard air sprayer includes an axial fan type of blower assembly which is horizontally mounted behind the spray tank on a sprayer trailer. An example of such a sprayer is the Model LV300 Air Sprayer manufactured and sold by the FMC Corporation, which corporation is the assignee of the present application. The axial fan type of sprayer delivers a spray solution with a relatively low velocity, high volume air blast, in comparison to the aforementioned centrifugal fan-type sprayer which delivers a spray solution with a relatively high velocity, low volume air blast. It should be noted that the axial fan type of sprayer is similar to the centrifugal fan type sprayer inasmuch as its air discharge openings are also arcuate in form and are oriented in a vertical plane to deliver a widely diverging air blast in a transverse direction relative to the path of movement of the sprayer.
In particular, the axial fan type of blower includes a cylindrical outer shell having an annular discharge ring at the front end thereof and a frustoconical diffuser mounted coaxially within the discharge ring in a spaced, parallel relationship therewith. The diffuser is truncated at its bottom end by a horizontal wall, and a pair of partitions are radially arranged between the diffuser and the discharge ring adjacent the top ends thereof. Thus, two arcuate discharge openings are formed at each side of the blower assembly between the diffuser and the discharge ring and between the bottom wall and the respective radially extending partitions. Such discharge openings are substantially similar to that of the aforedescribed centrifugal fan type of sprayer, but are much larger and deliver a greater volume of air. As in all air blast sprayers, including both the centrifugal and axial fan type, spray nozzles are positioned in the air discharge openings to deliver atomized spray solution to the air blast emanating therefrom. It has been found that the axial fan type of a sprayer also produces the "shingling" effect which reduces the penetration of the spray solution into the foliage and fruits of the plants being sprayed.
In both the centrifugal fan and the axial fan type of sprayers, the inlet openings of the blower assemblies are horizontally disposed and are relatively close to the ground. Thus, debris, dirt or other matter which is stirred up by the wheels of the trailer and tractor as the sprayer is drawn through the field can be drawn into the inlet opening. Such matter, when discharged in the air blast, tends to "sandblast" the foliage and fruits. To obviate this problem, the axial fan type of blower is sometimes provided with an air deflector positioned below the bottom end of the air inlet opening so as to divert debris and other matter from being directly drawn into such openings.